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Abstract:

A climatic chamber for rapidly reaching and maintaining a predetermined
air humidity and/or a predetermined temperature.
The air in a sample space is conveyable by at least one fan from an outlet
of sample space at least partially via a bypass branch and/or at least
partially via a drying branch back to an inlet of sample space.
The air is circulated continuously by the fans in a substantially
self-contained circuit. The air is guided by guide elements through the
bypass branch and/or drying branch.

Claims:

1. A climatic chamber for rapidly reaching and maintaining a predetermined
air humidity and/or a predetermined temperature, comprising at least one
fan wherein the air in a sample space is conveyable by said at least one
fan from an outlet of the sample space at least partially via at least
one of a bypass branch and a drying branch back to an inlet of the sample
space, wherein the air can be guided by at least one guide element at
least partially via at least one of the bypass branch and the drying
branch, wherein the guide elements are actuable by a control and
regulating device depending on at least one of a measured actual value of
the air humidity and a measured actual value of the temperature.

2. The climatic chamber according to claim 1, wherein, in order to rapidly
reach and maintain a predetermined setpoint value for the temperature in
the sample space, the temperature of the air is variable by a heating
and/or cooling device, wherein the temperature-regulating device being
arranged in the region of the inlet.

3. The climatic chamber according to claim 1, wherein at least one air
dehumidifier for drying the air is arranged in the drying branch.

4. The climatic chamber according to claim 3, wherein the air
dehumidifiers contain a desiccant.

5. The climatic chamber according to claim 1, wherein an ultrasound
evaporator is arranged in the bypass branch.

6. The climatic chamber according to claim 1, wherein at least one air
humidity sensor for determining the actual value of the air humidity in
the sample space is arranged in the region of the sample space.

7. The climatic chamber according to claim 1, wherein at least one
temperature sensor for determining the actual value of the temperature in
the sample space is arranged in the region of the sample space.

8. The climatic chamber according to claim 1, wherein the drying branch
and the bypass branch and the sample space form substantially closed
circuit for the circulation of the air, wherein the drying branch and the
bypass branch comprise closed conduits.

9. The climatic chamber according to claim 1, wherein the air can be
circulated continuously by the fans in a closed circuit.

10. A method for rapidly reaching and maintaining a predetermined air
humidity and/or a predetermined temperature in a climatic chamber
comprising:measuring an actual value of the air humidity in a sample
space of a climatic chamber, the climatic chamber comprising at least one
fan wherein the air in a sample space is conveyable by said at least one
fan from an outlet of the sample space at least partially via at least
one of a bypass branch and a drying branch back to an inlet of the sample
space, wherein the air can be guided by at least one guide element at
least partially via at least one of the bypass branch and the drying
branch, wherein the guide elements are actuable by a control and
regulating device depending on at least one of a measured actual value of
the air humidity and a measured actual value of the temperature; andat
least partially conveying the air via at least one of drying branch when
the actual value of the air humidity exceeds a predetermined setpoint
value for the air humidity in a sample space of the climatic chamber and
the bypass branch when the actual value of the air humidity reaches or
falls below the predetermined setpoint value for the air humidity in the
sample space.

11. The method according to claim 10, wherein the air is cooled by a
temperature-regulating device when the actual value of the temperature in
the sample space exceeds the predetermined setpoint value for the
temperature in the sample space.

12. The method according to claim 10, wherein the air is heated by the
temperature-regulating device when the measured actual value of the
temperature in the sample space falls below a predetermined setpoint
value for the temperature in the sample space.

13. The method according to claim 10, wherein the actual value of the air
humidity in the region of the sample space is measured with at least one
air humidity sensor.

14. The method according to claim 10, wherein the actual value of the
temperature in the region of the sample space is measured with at least
one temperature sensor.

15. The method according to claim 10, wherein the air is guided by at
least one guide element at least partially through the drying branch
and/or at least partially through the bypass branch.

16. The method according to claim 10, wherein guide elements are actuated
by a control and regulating device depending on the predetermined
setpoint values for at least one of the temperature and the air humidity
in the sample space as well as the measured actual values of at least one
of the air humidity and the temperature in the sample space.

17. The method according to claim 10, wherein at least one of the fans and
the temperature-regulating device are controlled depending on the
predetermined setpoint values for at least one of the temperature and/or
the air humidity in the sample space as well as the measured actual
values of at least one of the air humidity and the temperature in the
sample space.

18. The method according to claim 10 wherein the air is circulated
continuously by at least one fan from an outlet of the sample space at
least partially via at least one of the bypass branch the drying branch
back to an inlet of the sample space in a substantially closed circuit.

Description:

FIELD OF INVENTION

[0001]The invention relates to a climatic chamber for rapidly reaching and
maintaining a predetermined air humidity and/or a predetermined
temperature.

[0002]The invention also relates to a method for rapidly reaching and
maintaining a predetermined air humidity and/or a predetermined
temperature in a climatic chamber.

BACKGROUND OF THE INVENTION

[0003]A large number of test chambers or climatic chambers for
investigating material samples and suchlike are known. Defined
temperatures and/or a predetermined air humidity for a specific desired
climate can for example be produced in the sample space with such
climatic chambers.

[0004]Bound up with the known climatic chambers, however, is the drawback,
amongst other things, that a predetermined climate is established only
after a relatively long time. If, however, material samples are to be
subjected to a defined climate for only a short time, the material
samples often cannot remain for such a long time in the climatic chamber,
because the measurement results would otherwise be influenced by the
excessively long dwell time in the climatic chamber.

[0005]In order to bring the material samples into the sample space after
the predetermined climate has been reached, a sluice has to be provided
in the climatic chamber, said sluice increasing the design outlay
considerably.

[0006]On account of the generally long response times up to reaching a
predetermined climate, moreover, the number of investigations to be
carried out in the previously known climatic chambers is often limited.

SUMMARY OF INVENTION

[0007]There may be a need to provide a climatic chamber which avoids the
drawbacks of known embodiments of climatic chambers described above.

[0008]This need may be met by a climatic chamber with the features of
claim 1.

[0009]Due to the fact that the air in the sample space can be conveyed by
using at least one fan from an outlet of the sample space at least
partially via a bypass branch and/or at least partially via a drying
branch back to an inlet of the sample space, the air humidity and/or the
temperature in the sample space of the climatic chamber according to the
invention may be brought very rapidly and precisely to predetermined
values.

[0010]According to another exemplary embodiment of the climatic chamber,
the air is conveyable by at least one guide element at least partially
via the bypass branch and/or at least partially via the drying branch to
rapidly reach and maintain a predetermined setpoint value for the air
humidity in the sample space. An only partial diversion of the air stream
into the bypass branch may thus be possible, as a result of which the air
humidity in the sample space may be controlled more precisely.

[0011]According to another exemplary embodiment of the invention,
provision is made such that, in order to rapidly reach and maintain a
predetermined setpoint value for the temperature in the sample space, the
temperature of the air can be varied by a temperature-regulating device,
in particular by a heating and/or cooling device, the
temperature-regulating device being arranged in particular in the region
of the inlet.

[0012]The temperature-regulating device comprises a cooling device and can
additionally comprise a heating device. As a result of the zeolites
preferably used as a desiccant, the temperature in the sample space rises
as the air humidity is absorbed by the zeolites. This rise in the
temperature of the air in the sample space caused by the exothermic
reaction of the zeolites with the absorption of humidity is compensated
for by the cooling device, so that the air temperature in the sample
space remains essentially constant. The cooling device can be constituted
for example by Peltier elements or suchlike, through which the air stream
to be thermally regulated passes. By the optional heating device, the
temperature of the air in the sample space can, if required, be raised
above the value of the ambient air temperature and/or room temperature
independently of the effect of the zeolites. The heating device is
preferably operated electrically, so that easy regulatability results.
For example, the heating device can be constituted by helically arranged
resistance wires or suchlike through which the air stream flows.

[0013]Another exemplary embodiment makes provision such that the guide
element or guide elements can be actuated by a control and regulating
device depending on a measured actual value of the air humidity and/or
depending on a measured actual value of the temperature.

[0014]The control and regulating device may enable the predetermined air
humidity values and/or the predetermined temperature values in the sample
space of the climatic chamber to be reached and maintained largely
automatically.

[0015]According to another exemplary embodiment, at least one air
dehumidifier for drying the air is arranged in the drying branch.

[0016]The dehumidifier may enable a rapid and selective withdrawal of
moisture from the air stream and thus a reduction of the air humidity in
the sample space.

[0017]According to another exemplary embodiment of the climatic chamber,
the air dehumidifier contains or the air dehumidifiers contain a
desiccant, in particular zeolites or suchlike.

[0018]The zeolites preferably used as a desiccant may enable a rapid
reduction of the air humidity and have a preferably grainy consistency.
The zeolites can be accommodated for example in wide-mesh wire baskets,
the cross-sectional areas whereof preferably correspond roughly to the
cross-sectional area of the drying branch. The wire baskets are inserted
into the air dehumidifier, so that the air preferably flows through the
zeolites in the dehumidifier over the whole area. Moreover, the wire
baskets in the air dehumidifiers may enable rapid replacement of the
zeolites. The zeolites are capable of binding the moisture contained in
the air very tightly to themselves by physical processes within the
crystalline structure, but they can also be regenerated by the supply of
heat after complete saturation with moisture.

[0019]According to another exemplary embodiment of invention, an air
humidifier, in particular an ultrasound evaporator, is arranged in the
bypass branch.

[0020]The air humidifier may enable, if need be, a selective increase of
the air humidity in the air stream.

[0021]Moreover, the need may be met by a method which comprises:
[0022]measuring of an actual value of the air humidity in a sample space
of the climatic chamber and [0023]at least partial conveying of the air
via a drying branch when the actual value of the air humidity exceeds a
predetermined setpoint value for the air humidity in the sample space
and/or at least partial conveying of the air via a bypass branch when the
actual value of the air humidity reaches or falls below the predetermined
setpoint value for the air humidity in the sample space.

[0024]It may thus be ensured that a predetermined air humidity and/or
temperature is rapidly reached. In addition, once the values for the air
humidity and/or the temperature in the sample space are reached, they may
be maintained extremely precisely and over long periods.

[0025]According to another exemplary embodiment of the method, the air is
cooled by the temperature-regulating device when the actual value of the
temperature in the sample space exceeds the predetermined setpoint value.

[0026]If need be, the air may thus be cooled when the temperature of the
air rises for example following the absorption of air humidity in the
drying branch on account of the usually exothermic reaction of the
desiccant in the form of the zeolites.

[0027]According to another exemplary embodiment of the method according to
the invention, the air is heated by a temperature-regulating device when
a measured actual value of the temperature in the sample space falls
below a predetermined setpoint value.

[0028]By the optionally provided heating function of the
temperature-regulating device via an additional heating device, the
temperature of the air in the sample space may, if required, be raised
above the ambient air temperature or room temperature independently of
the effect of the zeolites, in order for example to reach a predetermined
air humidity value which, with a lower air temperature, would lead to an
undesired condensation of air humidity.

[0029]According to another exemplary embodiment of the method, the air is
guided by at least one guide element at least partially through the
drying branch and/or at least partially through the bypass branch.

[0030]This development may enable a very rapid and yet precise regulation
of the air humidity in the sample space by the simple actuation of the
guide elements.

[0031]Further advantageous developments of the climatic chamber and the
method are set out in the claims.

SHORT DESCRIPTION OF THE DRAWINGS

[0032]In the drawing:

[0033]FIG. 1 shows a diagrammatic representation of the climatic chamber
according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0034]FIG. 1 shows a diagrammatic representation of the mode of
functioning of the climatic chamber according to an exemplary embodiment
of the invention for rapidly reaching and maintaining a predetermined air
humidity and/or a predetermined temperature in a sample space.

[0035]Climatic chamber 1 comprises, amongst other things, a sample space
2, a bypass branch 3, and a drying branch 4. A fan 6 is located in the
region of an outlet 5 from sample space 2. The fan 6 conveys the air from
sample space 2 via an outlet elbow 7 in the direction of the directional
arrows represented with continuous lines into drying branch 4, since
guide elements 8, 9 in the position symbolised by continuous lines
essentially shut off bypass branch 3.

[0036]Guide elements 8, 9 can, as shown in FIG. 1, be constituted by
flaps. The flaps can be actuated for example by servomotors, actuating
motors or other actuators, controlled by a control and regulating device.
Instead of the flaps as guide elements 8, 9, other electrical or
pneumatically operated shut-off elements, such as for example valves,
slide valves, tyre valves or suchlike, can also be used as an
alternative.

[0037]Three air dehumidifiers 10, 11, 12 are arranged in drying branch 4.
A desiccant 13 is present in each case in air dehumidifiers 10, 11, 12.
As desiccant 13, use is preferably made of zeolites with a grainy
consistency, which bind the absorbed air humidity very tightly to
themselves and can be regenerated as often as desired by the supply of
heat. Desiccant 13 in the form of zeolites can thus be inserted into air
dehumidifiers 10, 11, 12, for example in wide-mesh, readily air-permeable
wire baskets. The wire baskets preferably have a cross sectional area
which roughly corresponds to the cross-sectional area of drying branch 4,
so that the air flows through desiccant 13 as completely as possible and
without major flow resistances. The wire baskets with desiccant 13
located therein also enable rapid replaceability of desiccant 13.

[0038]After flowing through air dehumidifiers 10, 11, 12, the air is
conveyed by a further fan 14 through an inlet elbow 15, a
temperature-regulating device 16 and an inlet 17 back into sample space
2. The air thus flows through climatic chamber 1 in an essentially
self-contained circuit. A sample 18 to be investigated in the climatic
chamber 1 is present in sample space 2.

[0039]By temperature-regulating device 16, the air is cooled, if need be,
in the region of inlet elbow 15, so that the temperature of the air can
be lowered in a selective manner. If temperature-regulating device 16 has
an optional heating device, the temperature in sample chamber 2 can also
be raised above the level of the ambient air temperature or room
temperature independently of the effect of the zeolites.

[0040]This may be necessary, for example, when it is intended to establish
an air humidity in climatic chamber 1 that lies above the saturation air
humidity at the current temperature in sample space 2. In this case, it
may be necessary to increase the temperature of the air in a selective
manner by the heating device, in order to avoid condensation of air
humidity in the climatic chamber 1 at the desired temperature and/or air
humidity in sample space 2.

[0041]Furthermore, when the zeolites as desiccant 13 absorb moisture, they
give off a part of the energy that has been supplied to them by heat
during the regeneration. The heat supply during the regeneration of
desiccant 13 brings about the complete reversible expulsion of the
moisture absorbed by desiccant 13, in particular the water or air
humidity, from the crystalline bond of the zeolites. As a result of the
absorption of air humidity, the zeolites forming desiccant 13 in air
dehumidifiers 10, 11, 12 and also, therefore, the air flowing through
desiccant 13 thus heat up, so that the air may have to be cooled down
again to the setpoint temperature of, for example, 23° C. by the
cooling device contained in temperature-regulating device 16. The cooling
function of temperature-regulating device 16 is generally always
required, in order to compensate for or even out the temperature
fluctuations of the air due to the absorption of air humidity by the
zeolites.

[0042]Temperature-regulating device 16 can for example be constituted by
Peltier elements as a cooling device, which are equally suitable for the
heating or the cooling of the air. Alternatively, temperature-regulating
device 16 can also comprise a separate heating and cooling device. In
this connection, electric heating elements in combination with an
absorber cooling device, compressor cooling device or suchlike, are
conceivable for constituting the temperature-regulating device. The
electric heating elements can be constituted by helically arranged
resistance wires or suchlike, for example.

[0043]It is not absolutely essential for temperature-regulating device 16
to have the possibility of additional heating of the air flowing through
sample space 2 by a heating device. In the case where a heating facility
is absent, the air in sample space 2 has a temperature that roughly
corresponds to the ambient air temperature and/or room temperature, so
that the climatic chamber 1 essentially corresponds in terms of its
function to an air dehumidifier with an extremely precise adjustment
facility for the degree of air humidity in sample space 2 and not to a
climatic chamber.

[0044]Temperature-regulating device 16, furthermore, is equipped with a
recooler 19 and a further fan 20. The recooler 19 serves in particular to
carry away waste heat from the cooling device of temperature-regulating
device 16 in the cooling operation. In order to intensify the recooling
effect, fan 20 is provided by which, if need be, ambient air is drawn by
suction through recooler 19. Furthermore, a control and regulating device
21 is provided.

[0045]The air humidity in sample space 2 falls rapidly in the position of
guide elements 8, 9 described above, because the air is conveyed almost
exclusively via drying branch 4.

[0046]If guide elements 8, 9 are swivelled into the position indicated
with broken lines, the path for the air through drying branch 4 is
essentially cut off. Guide elements 8, 9 move in the direction of the
small curved arrows provided on guide elements 8, 9. In this position of
guide elements 8, 9, air is conveyed almost exclusively via bypass line 3
along the directional arrows drawn dashed. In this position of guide
elements 8, 9, the air humidity in sample space 2 remains essentially
unchanged or at least it increases only very slowly, because the air is
now essentially conveyed solely via bypass branch 3. A significant
increase in air humidity in sample space 2 takes place in this position
of guide elements 8, 9 solely in the presence of a sample 18 with a high
moisture content and/or with actuation of an optional air humidifier (not
shown) by control and regulating device 21.

[0047]Furthermore, it is possible for guide elements 8, 9 to assume
intermediate positions, so that only a part of the air is conveyed via
drying branch 4 or bypass branch 3. A slower and therefore more precise
reduction of the air humidity in sample space 2 can thus be achieved. In
principle, it is to be assumed that guide elements 8, 9 are moved
simultaneously with one another, in order to avoid an undesired
backpressure of the air. Alternatively, the guide elements 8, 9 can also
be actuated independently of one another. The guide elements 8, 9 are
actuated by actuators (not shown), for example servomotors or suchlike.

[0048]Bypass branch 3, drying branch 4, outlet elbow 7 and inlet elbow 15
are preferably constituted by pipes or suchlike and represent together
with sample space 2 a self-contained circuit in the ideal case completely
separated from the ambient air, in which the air is continuously
circulated by fans 6, 14 during the period of investigation of the
sample. The ambient influence on climatic chamber 1 is thus minimised. In
a preferred embodiment of the climatic chamber 1 according to the
invention, the pipes have a diameter of less than 200 mm. Instead of the
pipes with an essentially circular cross-section described above, use can
also be made of air ducts or suchlike which, for example, have a
rectangular or square cross-section. Larger diameters than 200 mm are
also possible for the pipes.

[0049]In the following description, it will be assumed that the
temperature in sample space 2 is in principle measured in degrees Celsius
(° C.). The air humidity of the air in sample space 2 is
determined as relative air humidity in percentage (rel. hum. %). The
relative air humidity denotes the ratio in percentage between a maximum
quantity of water that can be absorbed in theory by the air at a specific
temperature to the quantity of water actually present in the air at the
time of the measurement.

[0050]At least one air humidity sensor 22 and at least one temperature
sensor 23 are preferably arranged in the sample space. The corresponding
measured values or actual values of the temperature and air humidity
currently prevailing in sample space 2 are ascertained by air humidity
sensor 22 and temperature sensor 23 and relayed via measurement lines
(not shown) to control and regulating device 21. Alternatively, further
air humidity sensors and/or further temperature sensors can be arranged
inside or outside sample space 2, in order to enable a more accurate
determination of the actual values for the temperature and the air
humidity so as to improve the control.

[0051]An arrangement of air humidity sensor 22 and temperature sensor 23
diverging from the representation of FIG. 1 is also possible. The air
humidity sensor 23 can be arranged for example in the region of inlet
elbow 15 or outlet elbow 7. Furthermore, air humidity sensors can be
arranged in the region of bypass branch 3 and/or drying branch 4. The
same also applies to the arrangement of temperature sensor 23. A
divergence deviation from the arrangement of air humidity sensor 22 and
temperature sensor 23 in sample space 2 shown by a way of example in FIG.
1 may be required for example in. order to adapt to specific test and
investigation conditions for sample 18.

[0052]Furthermore, climatic chamber 1 according to the invention comprises
input devices (not shown) with which setpoint values for the temperature
and air humidity to be reached and maintained in sample space 2 can be
predetermined by a user. The input devices can for example be rotary
regulators, switches, keys or suchlike. Furthermore, the climatic chamber
1 can comprise output devices, for example in the form of analog
displays, digital displays, communication interfaces or suchlike, which
display for example the current temperature values and air humidity
values in sample space 2 for a user. Furthermore, the climatic chamber 1
according to the invention can be equipped with a time-switch device,
which for example emits a signal after the lapse of a period,
predeterminable by a user, for the desired dwell time of sample 18 in
sample space 2.

[0053]The control and regulating device 21 controls all the sequences in
the climatic chamber 1 according to the invention. For this purpose,
guide elements 8, 9, temperature-regulating device 16 and fans 6, 14, 20,
amongst other things, are connected via control lines (not shown in FIG.
1) to control and regulating device 21. Corresponding to this, the air
humidity sensor 22 and the temperature sensor 23 are also connected via
measurements lines to control and regulating device 21. Furthermore, the
input devices and output devices for the user are connected to the
control and regulating device 21. The control and regulating device 21 is
preferably constituted by a standard computing unit, in particular by a
digital computer.

[0054]The term "rapidly reaching" a predetermined air humidity and/or
temperature in sample space 2 means that, with an initial air humidity
of, for example, 50% in sample space 2, the air humidity reaches a value
of less than 1% within a period of less than 30 seconds after starting up
climatic chamber 1. By the climatic chamber 1 according to the invention,
this value of the air humidity of less than 1% at a temperature of, for
example, 23° C. (room temperature, ambient air temperature) in
sample space 2 can in particular be reached rapidly and, in addition, be
maintained precisely over the duration of the test, i.e. can be held
essentially constant.

[0055]All in all, an extremely rapid and at the same time precise
adjustment and maintenance of an air humidity in sample space 2
predetermined by the user is in the first place made possible by the
climatic chamber 1 according to the invention. For this purpose,
temperature-regulating device 16 comprises in the first place a cooling
device. Moreover, a temperature in sample space 2 predetermined by the
user can be rapidly and precisely reached and maintained with a
temperature-regulating device 16 with a facility for beating the air
flowing through sample space 2 by a suitable heating device, said
temperature also being able to lie above the level of the ambient air
temperature or room temperature independently of the influence of the
zeolites.

[0056]According to the method according to an exemplary embodiment of the
invention, a user first predetermines the desired setpoint values for the
air humidity and/or the temperature in sample space 2 with the input
device. Sample 18 to be investigated is of course first introduced into
sample space 2.

[0057]The setpoint values predetermined by the user are recorded and
stored by the control and regulating device 21. If, for example, a user
predetermines a setpoint value of 23° C. for the temperature and a
setpoint value of 10% for the relative air humidity in sample space 2 by
the input devices, control and regulating device 21 seeks to reach these
values as rapidly as possible and then to keep them constant, in
particular by actuation of guide elements 8, 9, temperature-regulating
device 16 and fans 6, 14. The values currently prevailing in sample space
2, i.e. the actual values for the air humidity and/or the temperature,
are continuously determined by the air humidity sensor 22 and the
temperature sensor 23 and relayed via measurement lines to the control
and regulating device 21.

[0058]The precise sequence of the method according to the exemplary
embodiment of the invention will be explained below in greater detail
with the aid of the control process for the air humidity and the
corresponding control process for the temperature using the example of a
predetermined air humidity of 10% and a temperature of 23° C.,
which roughly corresponds to the ambient air temperature or room
temperature.

[0059]If the value of the current relative air humidity, i.e. the actual
value, in sample space 2 amounts for example to 50% initially, guide
elements 8, 9 are swivelled by control and regulating device 21 into the
position represented by the continuous lines, so that the air flows
almost exclusively through drying branch 4. The excess air humidity is
now rapidly extracted from the air by the zeolites contained as desiccant
13 in air dehumidifiers 10, 11, 12, so that the air humidity in sample
space 2 begins to fall. The current air humidity in sample space 2 is
constantly determined by air humidity sensor 22.

[0060]Guide elements 8,9 can assume arbitrary "intermediate positions" and
are not limited to the completely opened or closed position represented
by way of example in the illustration of FIG. 1. The term "intermediate
position" means in this connection that a volume flow proportion between
0% in 100% of the total air stream can be conveyed both through bypass
branch 3 and drying branch 4 depending on the position of guide elements
8, 9, wherein the sum of the volume flow proportions of the
sub-airstreams in drying branch 4 and in bypass branch 3 always amounting
to 100%.

[0061]The movement of guide elements 8, 9 preferably takes place by
so-called "servomotors", which permit arbitrary positions and/or
arbitrary "intermediate positions" of guide elements 8, 9, preferably
designed as flaps, under the control of control and regulating device 21.

[0062]The position of guide elements 8, 9 is varied by control and
regulating device 21 during the actual control process until such time as
the actual value of the air humidity in sample space 2, apart from a
tolerable control deviation, is roughly equal to the predetermined
setpoint value of 10% for the air humidity. If sample 18 has a high
moisture content, guide elements 8, 9 are also opened wide by control and
regulating device 21, in order to reach more rapidly the setpoint value
of the air humidity by conveying a large volume flow of air through
drying branch 4. If, on the other hand, sample 18 has a lower moisture
content, the amplitudes of the movements of guide elements 8, 9 are
reduced, controlled by the control and regulating device, in order to
avoid overswings of the control process and to reach the setpoint value
more rapidly.

[0063]Once the setpoint value has been reached, guide elements 8, 9 can be
swivelled by control and regulating device 21 into the position
represented by the broken line, so that the air is now essentially
conveyed exclusively via bypass branch 3 and the air humidity in sample
space 2 remains constant.

[0064]Preferably, however, guide elements 8, 9 are located in a "middle
position" when the setpoint value of the air humidity in sample space 2,
minus a control tolerance, has been reached, in order in particular to
enable a more rapid compensation with renewed fluctuations of the air
humidity.

[0065]If the value of the air humidity prevailing in sample space 2
changes again from 10% due to external influences and/or due to the
influence of sample 18, the air humidity is again brought to the
predetermined setpoint value of 10% by means of drying branch 4 and a
corresponding adjustment of guide elements 8, 9, controlled by control
and regulating device 21.

[0066]If the current value of the temperature of the air in sample space 2
amounts for example to 18° C., this temperature value is
determined by temperature sensor 23 and relayed to control and regulating
device 21. The actual value of the temperature in sample space 2, minus a
control tolerance, is thus smaller than the setpoint value of 23°
C. predetermined by the user, so that the air is heated by the
temperature-regulating device 16 until such time as the actual value of
the temperature again corresponds to the setpoint value of 23° C.,
minus a control tolerance. An increase in the temperature of the air in
sample space 2 above the level of the ambient air temperature or room
temperature independently of the effect of the zeolites is as a rule only
possible if temperature-regulating device 16, as has already been
described above, comprises the optional facility of heating by a heating
device, for example in the form of electrically operated heating elements
or suchlike.

[0067]If the exothermic reaction of the zeolites shall be used for
indirect "heating" of the air in sample space 2, it needs to be taken
into account that, as a result of this, the air humidity in sample space
2 may possibly again change in an undesired manner.

[0068]If, on the other hand, the actual value of the temperature of the
air in sample space 2 is greater than the predetermined setpoint value of
23° C., the air is cooled by the cooling device of
temperature-regulating device 16 until such time as the setpoint value of
the temperature of 23° C., minus a control tolerance, has been
reached. In its mode of functioning, the control process for the
temperature of the air corresponds in principle to the control process
for the air humidity.

[0069]Both the control process for the air humidity and the control
process for the temperature are controlled in parallel, or matched to one
another, by control and regulating device 21. Moreover, it may also be
necessary to control, in a suitable manner by the control and regulating
device 21, fans 6, 14 which circulate the air inside climatic chamber 1,
in order for example to lessen or intensify the drying process in drying
branch 4 and/or the heating or cooling of the air in
temperature-regulating device 16. This control of fans 6, 14 can take
place for example by a speed regulator and/or an adjustment of the
setting angle of the fan rotors. The same applies to fan 20.

[0070]The overall control process is relatively expensive on account of
the control processes for the air humidity and the temperature to be
performed in parallel, so that the implementation of the control takes
place preferably using software by the control and regulating device 21.
Alternatively, the control can also take place with analog circuits.

[0071]On account of the forced circulation of the air by the fans 6, 14 in
combination with the rapid change-over facility between bypass branch 3
and drying branch 4, it is possible by the method according to the
invention for a temperature and/or air humidity in climatic chamber 1
predetermined by the user to be maintained quickly and in addition very
precisely over the whole test duration, i.e. to be held constant for the
most part.

[0072]It should be noted that the term "comprising" does not exclude other
elements or steps and the "a" or "an" does not exclude a plurality. Also
elements described in association with different embodiments may be
combined. It should also be noted that reference signs in the claims
shall not be construed as limiting the scope of the claims.